The present invention generally relates to lens caps for transistor outline packages adapted to package optoelectronic components, and particularly to ball lens caps for said transistor outline packages.
Optoelectronic components, such as optical coupling devices, generally require a lens cap to protect them from damage and from EMI (Electro Magnetic Interference). Without such protection, damage can result from exposure to moisture, dirt, heat, radiation, or other hazards. The lens cap generally comprises a main part and a lens part. The lens part is usually coupled to the main part by gluing, as disclosed in Japanese Application 2-165684However, the lens part is often contaminated by dispersion of the glue and then its optical characteristics are affected. In addition, there is a danger that the lens part will become separated from the main part of the housing if the glue loses effectiveness over time. Furthermore, the lens cap is unduly costly due to its time-consuming manufacturing method.
Therefore, an improved lens cap for a transistor outline package that overcomes the above-mentioned disadvantages is desired.
A main object of the present invention is to provide a lens cap for a transistor outline package which holds up over time and whose optical characteristics are reliably good.
Another object of the present invention is to provide a cheap lens cap for a transistor outline package which is suitable for mass production.
To achieve the above objects, a lens cap for a transistor outline package comprises a lens part and a hollow main part adapted for receiving optoelectronic components. The lens part includes a ball lens having a first groove and a sprue filling portion having a second groove. The main part defines an opening which comprises a ball lens receiving hole communicating with a sprue. A sidestep is formed along an edge of the opening protruding into the sprue. The ball lens has a diameter greater than the ball lens receiving hole. The lens part is thus firmly coupled to the main part of the lens cap through the engagement of the protruding sidestep with the second groove and a circular rim of the main part with the first groove.